Considerable effort has been spent trying to perfect a socket wrench having two modes of operation that can be used independently or simultaneously. Some factors that have greatly limited the success of these efforts are ratchet mechanism location, the type of ratchet mechanism used and handle mounting and retention.
The prior art of Singleton (U.S. Pat. No. 4,907,476) is an example of ratchet mechanism location effecting handle and ratchet mechanism operation. In that prior art, the ratchet mechanism is in the head, allowing the wrench to be rotated and repositioned as is a common socket wrench, but the t-handle can only be rotated in one direction and not repositioned. This is due to the fact that the ratchet mechanism in the head only allows rotation in one direction relative to the head. When the t-handle is turned, the ratchet pawls disengage to allow rotation relative to the head but when attempting to reposition the t-handle in the other direction, the ratchet pawls now engage, blocking rotation. This also means that when using the socket wrench in the common manner, anytime the socket rotates relative to the head (i.e. repositioning), it causes the t-handle to rotate again. Several prior art attempts have been made to improve this situation by adding a second ratchet mechanism, including Gegg (U.S. Pat. Nos. 3,952,617 and 5,201,255) and Scott (U.S. Pat. No. 4,474,089). This resulted in wrenches of great complexity and a high number of custom parts that can have a detrimental impact on assembly and production. Further, the prior art of Cockman, Jr. (U.S. Pat. No. 4,406,184) teaches that by locating a single ratchet mechanism in the handle, completely disconnected from the head, two modes of operation can be achieved simultaneously, making a second ratchet mechanism unnecessary.
While Cockman, Jr. (U.S. Pat. No. 4,406,184) taught ratchet mechanism location, its efforts to provide sufficient means to retain the handle had questionable results at best. A handle that is required to move along the longitudinal axis of the socket wrench to lock, it seems, could just as easily become unlocked when the forces applied to the handle are not completely perpendicular to the handle. This situation may cause the handle to suddenly come unlocked, the handle retaining screw to impact the side of its slot, subjecting it to considerable side loads, and more likely than not causing eventual failure of the handle retaining screw.
It is apparent that some have tried to overcome these obstacles by what amounts to interconnecting a right-angle driver extension to a type of ratcheting screwdriver. Again, handle retention becomes a significant problem. The methods employed to retain a screwdriver handle are designed to deal with rather small rotational forces and quickly fail when placed under heavy side loading. It would appear that some have tried to downplay the issue. Prior art Huang (U.S. Pat. No. 7,069,818), Gegg (U.S. Pat. No. 5,201,255), Scott (U.S. Pat. No. 4,474,089) and Cockman, Jr. (U.S. Pat. No. 4,406,184), to name a few, all lack, in this writers opinion, a quickly discernable, proven method of handle retention that is capable of withstanding the loads encountered when using a socket wrench in the described manners.
Another problem with the ratcheting screwdriver solution is the selection of ratchet mechanisms. Typically, a socket wrench contains a ratchet mechanism able to endure greater loads than any found in a ratcheting screwdriver. The ratchet mechanisms typically found in socket wrenches also have a greater number of teeth meaning that the socket wrench can be rotated and repositioned in as little as six to nine degrees of movement. A typical ratcheting screwdriver may require eighteen degrees of movement to be repositioned. This situation becomes apparent in prior art Huang (U.S. Pat. No. 7,069,818), forcing the use of gear reduction in the head to compensate for this predicament.
Another problem to consider is deflection and/or bending. When side loading the handle, if the load is conveyed directly to the drive shaft or some type of coupling device, there is a great possibility that the shaft or coupler will become jammed, distorted or bent, leaving the tool inoperable. Obviously, a socket wrench of the type described, needs some form of structure to withstand the loads encountered in everyday use.
Prior art Cockman, Jr. (U.S. Pat. No. 4,406,184) also taught the use of a means to lock the handle in position relative to the wrench itself. Because the handle and the ring gear for the ratchet mechanism rotate as one, when the tool is rotated around the axis of the socket to input torque in common fashion, the ratchet mechanism pawl engages the ring gear causing the handle to rotate in the opposite direction of the tool itself. Under relatively light loads this tendency can be opposed manually simply by the user holding the handle in position but under heavier loads there is a need to mechanically hold the handle in position. Again, a handle that is able to move along the axis of the wrench, it seems, could easily become disengaged from the desired setting, having a severe impact on tool function.